Device for controlling the volume of a car radio as a function of driving noise

ABSTRACT

In a device for controlling the volume of a car radio as a function of driving noise, an acceleration sensor can be mechanically connected with the body of the motor vehicle, to generate a signal dependent on driving noise.

FIELD OF THE INVENTION

The present invention relates to a device for controlling the volume ofa car radio as a function of driving noise.

The noise level inside a motor vehicle is greatly dependent on the speedat which the vehicle is being driven in each instance. Since manualadjustment of the volume of a car radio to this noise level isconsidered bothersome, various methods for controlling the volume of acar radio as a function of the driving noise have already become known.From German Patent Application No. DE-A-33 38 413, a circuit arrangementfor automatic noise-dependent volume control in a motor vehicle isknown, where a signal which represents the interference in the carinterior is generated using a microphone affixed in the car interior. Tocompensate the audio signal component in the microphone output signalgenerated by the loudspeaker signal, the loudspeaker input signal issubtracted from the microphone output signal in a summation circuit, sothat a control value in the form of the interference noise level presentin the vehicle interior is present at the output of the subtractionelement.

From European Patent Application No. EP-A-0 246 772, an arrangement toattenuate body vibrations in motor vehicles is known, where thevibrations are caused, for example, by driving over uneven areas in theroad. For this purpose, the body vibrations are detected using anacceleration-sensor, and the measurement signal is evaluated in acomputer unit. The chassis shock absorbers of the vehicle are tuned, asa function of the measurement signal, in such a way that body vibrationsare reduced.

It is the task of the present invention to improve the derivation of asignal dependent on driving noise, which is used to control the volumeof a car radio as a function of driving noise, in such a way thatmeasures to remove wanted signal components from the control signals arenot necessary.

This task is accomplished, according to the invention, in that anacceleration sensor can be mechanically connected with the body of themotor vehicle, to generate a signal dependent on driving noise. In thisconnection, it can be provided, as a simplification, that theacceleration sensor essentially measures vertical accelerations.

The present invention is based on the recognition that driving noisesare transferred into the interior (passenger space) of the motor vehiclemainly as structure-borne noise. These noises are, in particular, enginenoises and tire noises. Measures to remove the wanted signal componentfrom the signal obtained using the acceleration sensor are not neededfor the device according to the present invention.

The device according to the present invention demonstrates theadditional advantage, particularly if the acceleration sensor isarranged in the car radio, according to a further development, that nofurther installations are required within the vehicle itself--such aslaying lines and installing a microphone.

Preferably, it is provided, for the device according to the invention,that the acceleration sensor is rigidly connected with the housing ofthe car radio. An advantageous development of the device according tothe present invention consists of the fact that the acceleration sensordemonstrates a signal band width of about 1 kHz. This covers the entirespectral range required for masking structure-borne noise, andcommercially available acceleration sensors can be used, such as theacceleration sensor Type ADXL50 from the company Analog Devices.

Although the device according to the present invention is also suitable,for example, for volume control independent of frequency, better resultsare obtained with frequency-dependent masking, for which it is provided,according to a further development of the device according to thepresent invention, that an output of the acceleration sensor can bepassed to a multi-channel equalizer, via a signal processing circuitwith a known, predetermined algorithm, along with the audio signalsgenerated by the car radio, the outputs of which equalizer are connectedwith control inputs of the signal processing circuit and with inputs ofend stages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a motor vehicle with a device according to the presentinvention.

FIG. 2 shows a car radio with an acceleration sensor arranged on thebottom housing wall.

FIG. 3 shows a schematic of a device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The same parts are indicated with the same reference symbols in thedifferent figures.

FIG. 1 schematically shows a car with a body 1, front wheels 2, rearwheels 3, an engine 4 and a car radio 5, the loudspeakers 6, 7 of whichare only indicated. Double arrows illustrate the forces which act on thewheels and the forces which proceed from the engine and act on the body.It is evident that forces with a vertical effect make up a significantcomponent of the structure-borne noise. An acceleration sensor 8 istherefore arranged in such a way that it detects the verticalacceleration.

According to FIG. 2, the acceleration sensor 8 is arranged, for example,on the base plate of the car radio 5. It can therefore be connected withthe circuitry of the car radio in simple manner.

FIG. 3 shows a schematic of a device according to the present invention,in which the parts of the car radio which are not specifically adaptedto the invention, such as the receiver section, and cassette player,stereo decoder, and low frequency amplifier, if present, are comprisedin a circuit 11 as the low frequency source. The low frequency source 11passes the audio signals L and R to a multi-channel equalizer 12, whichis connected with four end stages 13, 14, 15, 16 for four loudspeakers17, 18, 19, 20 via four outputs. In this connection, LF and RF stand forthe signals for the left front and right front loudspeakers, while thesignals LR and RR indicate the signals for the left rear and right rearloudspeakers. The end stages 14 and 15 each invert the output signal, asindicated by a minus sign.

The output signal of the acceleration sensor 8 is passed, for example,to a signal processing circuit 21, which can be controlled by the outputsignals of the multi-channel equalizer 12. The signal processing circuit21 processes the output signal of the acceleration sensor and the outputsignals of the multi-channel equalizer with known algorithms. The outputsignal of the signal processing circuit is then passed to themulti-channel equalizer 12, in order to control amplification of theaudio signals L and F in several different frequency bands.

What is claimed is:
 1. A device for controlling a volume of a car radioof a motor vehicle as a function of a driving noise, comprising:anacceleration sensor detecting the driving noise which is provided intoan interior of the motor vehicle as a structure-borne noise andgenerating a sensor signal which relates to the structure-borne noise,the acceleration sensor being mechanically connected to a body of themotor vehicle; and a signal processing circuit receiving the sensorsignal and controlling the volume of the car radio disposed in the motorvehicle as a function of the sensor signal.
 2. The device according toclaim 1, wherein the acceleration sensor measures verticalaccelerations.
 3. The device according to claim 1, wherein theacceleration sensor is disposed in the car radio.
 4. The deviceaccording to claim 3, wherein the acceleration sensor is rigidlyconnected with a housing of the car radio.
 5. The device according toclaim 1, wherein the acceleration sensor demonstrates a signal band ofabout 1 Khz.
 6. A device for controlling a volume of a car radio of amotor vehicle as a function of a driving noise, comprising:anacceleration sensor detecting the driving noise which is provided intoan interior of the motor vehicle as a structure-borne noise andgenerating a sensor signal which relates to the structure-borne noise,the acceleration sensor being mechanically connected to a body of themotor vehicle; mechanically connected to a body of the motor vehicle; alow frequency source having an audio signal output; a multi-channelequalizer having a plurality of inputs and a plurality of outputs, theplurality of outputs being connected to a plurality of end stages, atleast one of the plurality of inputs receiving the audio signal outputfrom the low frequency source; and a signal processing circuit connectedto at least one of the plurality of inputs of the multi-channelequalizer and to the plurality of outputs of the multi-channelequalizer, the signal processing circuit receiving the sensor signal endcontrolling the volume of the car radio as a function of the sensorsignal and the outputs of the multi-channel equalizer via apre-determined algorithm.
 7. The device according to claim 6, whereinthe acceleration sensor measures vertical accelerations.
 8. The deviceaccording to claim 6, wherein the acceleration sensor is disposed in thecar radio.
 9. The device according to claim 6, wherein the accelerationsensor is rigidly connected with a housing of the car radio.
 10. Thedevice according to claim 6, wherein the acceleration sensordemonstrates a signal band of about 1 Khz.